// Copyright 2007. Adobe Systems Incorporated. All Rights Reserved.
package fl.accessibility {
	
	import fl.controls.Button;
	import fl.core.UIComponent;
	
	/**
	 *  The ButtonAccImpl class, also called the Button Accessibility Implementation class, 
	 *  enables communication between a Button component and a screen reader. Screen readers are used 
	 *  to translate screen content into synthesized speech or braille for visually impaired users.
	 * 
	 * <p>The ButtonAccImpl class supports system roles, Dynamic-based events, and states.</p> 
	 * 
	 * <p>A Button reports the role <code>ROLE_SYSTEM_PUSHBUTTON</code> (0x2B) to a screen 
	 * reader.</p>
     *
	 * <p>A Button reports the following states to a screen reader:</p>
	 * <ul>
	 *     <li><code>STATE_SYSTEM_NORMAL</code> (0x00000000)</li>
	 *     <li><code>STATE_SYSTEM_UNAVAILABLE</code> (0x00000001)</li>
	 *     <li><code>STATE_SYSTEM_FOCUSED</code> (0x00000004)</li>
	 *     <li><code>STATE_SYSTEM_PRESSED</code> (0x00000008)</li>
	 *     <li><code>STATE_SYSTEM_FOCUSABLE</code> (0x00100000)</li>
	 * </ul>
     *
	 * <p>A Button dispatches the following events to a screen reader:</p>
	 * <ul>
	 *     <li><code>EVENT_OBJECT_STATECHANGE</code> (0x800A)</li>
	 *     <li><code>EVENT_OBJECT_NAMECHANGE</code> (0x800C)</li>
	 * </ul>
	 * 
	 * <p>The user of a screen reader can activate a button component by using the spacebar or the Enter key.</p>
	 * 
     * @see fl.controls.Button Button
     *
     * @langversion 3.0
     * @playerversion Flash 9.0.28.0
	 *  
	 *  @playerversion AIR 1.0
	 *  @productversion Flash CS3
	 */
	extern public class ButtonAccImpl extends LabelButtonAccImpl {
		/**
		 *  @private
         *
         *  Static variable triggering the <code>hookAccessibility()</code> method.
		 *  This is used for initializing ButtonAccImpl class to hook its
         *  <code>createAccessibilityImplementation()</code> method to Button class 
         *  before it gets called from UIComponent.
         *
         * @langversion 3.0
         * @playerversion Flash 9.0.28.0
		 */
		private static var accessibilityHooked:Bool = hookAccessibility();
	
		/**
		 *  @private
         *
         *  Static method for swapping the <code>createAccessibilityImplementation()</code>
         *  method of Button with the ButtonAccImpl class.
         *
         * @langversion 3.0
         * @playerversion Flash 9.0.28.0
		 */
		private static function hookAccessibility():Bool {
			Button.createAccessibilityImplementation = createAccessibilityImplementation;
			return true;
		}
	
		//--------------------------------------------------------------------------
		//  Class methods
		//--------------------------------------------------------------------------
	
		/**
		 *  @private
		 *  Method for creating the Accessibility class.
		 *  This method is called from UIComponent.
		 * 
		 *  @param component The UIComponent instance that this AccImpl instance
		 *  is making accessible.
         *
         * @langversion 3.0
         * @playerversion Flash 9.0.28.0
		 */
		public static function createAccessibilityImplementation(component:UIComponent):Void {
			component.accessibilityImplementation = new ButtonAccImpl(component);
		}
	
		/**
         * Enables accessibility for a Button component.
		 * This method is required for the compiler to activate
		 * the accessibility classes for a component.
		 * 
         * @langversion 3.0
         * @playerversion Flash 9.0.28.0
		 *  
		 *  @playerversion AIR 1.0
		 *  @productversion Flash CS3
		 */
		public static function enableAccessibility():Void {
		}
	
		//--------------------------------------------------------------------------
		//  Constructor
		//--------------------------------------------------------------------------
	
        /**
         * @private
         * @internal Nivesh says: I don't think we should document the constructors 
         *           for the accessibility classes.  End-users just have to call the 
         *           static enableAccessibility method.  They don't really create an 
         *           instance of the classes.
         *
		 *  Creates a ButtonAccImpl instance for the specified Button component.
		 *
		 *  @param component The Button instance that this ButtonAccImpl instance
		 *         makes accessible.
		 *  
         * @langversion 3.0
         * @playerversion Flash 9.0.28.0
		 */
		public function ButtonAccImpl(component:UIComponent) {
			super(component);
			role = 0x2B;
		}
	}
}
